The present disclosure relates to a toner dispersing mechanism, a developing device including the toner dispersing mechanism, and an image forming apparatus, the toner dispersing mechanism being mounted to an electrophotographic image forming apparatus such as a copier, a printer, and a facsimile, and dispersing toner to be replenished from a toner storage container such as a hopper and a container into a developing device.
Conventionally, for facilitation of maintenance, a developing device to be mounted to an image forming apparatus is filled in advance with a predetermined amount of toner, and the whole developing device is replaced after the toner is depleted. However, the developing device cannot be frequently replaced from an economic viewpoint, and hence a toner capacity is inevitably increased for performing image formation on somewhat many sheets. Thus, it is difficult to downsize the developing device configured as described above. Under the circumstance, in order to achieve downsizing of the developing device, there has been proposed a developing device of a type in which toner is supplied from an outside.
Disadvantageously, in the developing device of such a toner supply type, a lump of toner is sometimes replenished into the developing device when toner fluidity is reduced depending on use environments and the like. Thus, there is a risk that the mixing properties with respect to developer existing in the developing device is deteriorated and a developer thin layer to be formed on a developing roller is disturbed, with the result that image failures such as image-density unevenness and fogging occur.
Under the circumstance, there have been proposed various techniques for suppressing occurrence of the image failures through in-advance dispersion of the toner to be replenished into the developing device. For example, there has been known a developing device in which a matrix member (mesh) and a brush-like developer supply roller are arranged between a developer carrier and a developer storage portion. Further, there has been known another developing device including a toner-replenishing-port stirring member for stirring toner in a toner replenishing port of a toner hopper. Still further, there has been known a method in which a toner dispersing member formed of a core and a cylindrical foam member is arranged to close a replenishing port of a toner bottle, and toner is dropped little by little into a developing device by rotating the toner dispersing member.
Meanwhile, there has been known an image forming apparatus which includes an auxiliary stirring container for separately receiving toner to be replenished from a toner replenishing container and carrier to be replenished from a carrier replenishing container and for sufficiently mixing and stirring the toner and the carrier with use of a screw-like stirring-and-conveying member, and in which developer, which is stabilized in charging properties by being preliminarily mixed in the auxiliary stirring container, is supplied to the developing device.
However, as for the developing device in which the matrix member (mesh) and the brush-like developer supply roller are arranged between the developer carrier and the developer storage portion, in a case where toner has been aggregated depending on use environments or owing to mechanical stress, clogging of the mesh member and fusion of the toner are liable to occur, and hence it is difficult to replenish toner by a minute amount. Further, as for the developing device including the toner-replenishing-port stirring member for stirring toner in the toner replenishing port of the toner hopper, an advantage of smoothly conveying the toner by breaking a bridge formed by aggregation of the toner in the toner replenishing port can be expected. However, it is difficult to completely disperse the lump of toner, and hence the above-mentioned problem has not yet been completely solved even with this device.
Meanwhile, as for the method in which the toner dispersing member formed of the core and the cylindrical foam member is arranged to close the replenishing port of the toner bottle, and toner is dropped little by little into the developing device by rotating the toner dispersing member, the toner dispersing member is attached on the toner bottle side. Thus, the toner dispersing member is replaced simultaneously with replacement of the toner bottle, which leads to a problem of a cost increase. Further, the cylindrical foam member is used as the toner dispersing member, and hence toner clogs the foam member, which leads to another problem of deterioration of durability of the toner dispersing member.
Further, although the auxiliary stirring container including the screw-like stirring-and-conveying member has a function of efficiently mixing and stirring toner and carrier, an advantage of dispersing aggregated toner into particles cannot be expected. Thus, the auxiliary stirring container has not been usable as a toner dispersing mechanism.